Feature telephone sets (sets which can provide a display of status of calls and special functions associated with a call, such as a hold status) can provide only limited indication to a user as to the status of calls. For example, a set used in a key telephone system may have several lines that it may use. When one of the lines is busy, a light located adjacent a push button associated with the line lights up. However there is no indication that a call is actually in progress or who are the parties to the call, but merely that a line is in use.
If a caller has placed a call on one line on hold, and has made one or more other calls on other lines which have also been placed on hold, lights associated with each of the lines may flash as a reminder that a line is on hold. However there is no indication which subscriber is on hold on any particular line. It is often difficult to remember which call on hold belongs to which party. In such cases the user may retrieve a call from hold and address the party by the wrong name, thinking that it is a party relating to another call on hold.
When a conference call is to be made and several conferees are placed on hold, and the local user wishes to have a private conversation with one or more of the conferees but to exclude others, mistakes can be made when taking subscribers off hold and into the private conversation with sometimes embarrasing or costly results if the local user is unaware that an undesired other party can hear the private conversation.
The above problem results because it is often difficult to remember which conferee is associated with a particular line. When a conferee is to be dropped from conference call, it is easy to make a mistake and to drop the wrong conferee line from the conference.
Special feature telephones and certain PBXs and key telephone systems can provide means that attempt to help the user that has callers are on hold somewhat by reminding the user that calls are on hold, by ringing the user's telephone after a certain time period following an incoming call being placed on hold. However this does not solve the problem of the user not knowing which party is on which held line, and therefore which line should be dropped from a conference or retreived from hold.